Fuel log producing apparatus



Feb. 1, 1966 R. J. SANDERS 3,232,722

FUEL LOG PRODUCING APPARATUS Filed Oct. 16. 1961 3 Sheets-Sheet 1 RAYMOND JOHN SAND RS Feb. 1, 1966 R. J. SANDERS FUEL LOG PRODUCING APPARATUS 3 Sheets-Sheet 2 Filed Oct. 16, 1961 mN..,m WW b w/ o m A R mm 1966 R. J. SANDERS 3,232,722

FUEL LOG PRODUCING APPARATUS Filed Oct. 16. 1961 3 Sheets-Sheet 5 IN l/E/V TOE RAYMOND JOHN SANDERS United States Patent 3,232,722 FUEL LOG PRODUCING APPARATUS Raymond John Sanders, Vancouver, British Columbia,

Canada, assignor to British Columbia Research Council, Vancouver, British Columbia, Canada,

Filed Oct. 16, 1961, Ser. No. 145,264 10 Claims. (Cl. 44-13) This invention relates to apparatus for producing fuel logs from iigno-cellulosic material in particulate form, and particularly wood sawdust, Chips and the like.

This apparatus may be used to produce fuel logs from ligno-cellulosic material in particulate form, such as wood, bagasse, seed hulls and the like, but is primarily designed for producing logs from wet sawdust, chips and the like.

A process for making fuel logs from wet cellulosic material has been developed by B. H. Levelton, and is described in another application. The logs are mainly made from waste materials of saw mills, and such materials are usually quite wet. Sawdust logs have been made for a great many years, but in each case it was necessary to dry the sawdust or chips before compressing them into fuel logs. The drying step was comparatively costly, a waste of time and required expensive equipment. The novel process not only eliminates the necessity of drying the material before forming the logs, but it results in logs that are vastly superior to those of the prior art. The prior fuel logs all have the disadvantage that they are not moisture stable. If the prior logs get wet or are even exposed to a damp atmosphere, they tend to disintegrate, and so great care must be exercised to keep them dry, and they cannot be stored for any length of time in a moist atmosphere, such as in damp basements. The logs produced by the novel process are water stable, and can actually be immersed in water or left in a damp atmosphere for long periods without disintegrating.

In order to be successful, the novel process requires the use of wet cellulosic material. However, the water present makes it impossible to produce fuel logs with the equipment of the prior art for this purpose. Another problem is to be able to produce fuel logs continuously while getting rid of excess moisture during the operation.

The main object of the present invention is the provision of apparatus for continuously forming fuel logs from wet cellulosic material while getting rid of excess moisture without interrupting the operation.

High pressure is used to compact the particulate material into a continuous log, and to generate an adequate temperature for carrying out the process. The compaction of the material results in excess moisture being squeezed out. The present apparatus is designed to let the excess moisture out with-out interfering with the continuous formation of the log.

A preferred form of the invention is illustrated in the accompanying drawings, in which FIGURE 1 is a reduced plan view of apparatus for producing fuel logs,

FIGURE 2 is an enlarged longitudinal sectional view taken on the line 22 of FIGURE 1,

FIGURE 3 is an enlarged longitudinal sectional view taken on the line 3-3 of FIGURE 1,

FIGURE 4 is a cross section on the line 4-4 of FIG- URE 2,

FIGURE 5 is a cross section on the line 55 of FIG- URE 2, and

FIGURE 6 is a cross section on the line 6-6 of FIG- URE 2.

Referring to the drawings, 10 is apparatus for producing fuel logs. This apparatus includes an extrusion or feed sleeve 11 having an internal bore 12. A plurality of circumferentially spaced keys 13 extend longitudinally of the inner surface of sleeve 11 and project radially into bore 12. Sleeve 11 has a discharge end 15 which is formed into a throat 16 having a smaller inner diameter than bore 12. Keys 13 extend to throat 16.

An extruder screw 22 is rotatably mounted in and extends heyond the opposite ends of sleeve 11. This screw just clears the inner surfaces of keys 13 and the inner surface of throat 15, as clearly shown in FIGURE 2. Screw 22 is supported and rotated in any desired manner. In this example, the cylindrical end 24 of screw 22 fits into a hollow shaft 25 and is driven by means of a key 26. Shaft 25 is carried by bearings 28 and 30. Bearing 32 is provided for taking the axial thrust created by screw 22 during operation. This shaft and bearings 28, 30 and 32 are positioned within a main housing 34. Shaft 25 is rotated in any desired manner. In this example, the shaft projects beyond the end of housing 34, and a pulley, sprocket or gear, not shown, is mounted on the projecting end of the shaft and is driven in any desired manner. This rotates screw 22 within sleeve 11.

Wet wood sawdust, chips or the like, or other cellulosic material, is fed to screw 22 at a point remote from throat 16 of sleeve 11. In this example, a passage 36 is formed in housing 34, see FIGURES 2 and 4, and is shaped to direct cellulosic material on to the top of screw 22. This material may be fed into passage 36 in any desired manner. For example, a simple screw conveyor 37 may be used to discharge into passage 35, said conveyor extending from a suitable hopper 38, see FIGURE 1.

The wet cellulosic material, which will hereinafter be called sawdust for the sake of convenience, is fed through passage 36 to screw 22. This screw moves the sawdust longitudinally through bore 12 of sleeve 11. Keys 13 prevent the sawdust from turning circumferentially with the screw, and keep it moving longitudinally in the sleeve.

A gear box assembly surrounds sleeve 11 and is secured to the adjacent end of housing 34 in any convenient manner, such as by cap screws 52. The assembly '50 includes a stator sleeve 54 which is coaxial with sleeve 11. Sleeve 54 has an entrance end 55 and an outlet end 56. The diameter of entrance 55 is greater than that of throat 16 of sleeve 11, and the bore 58 of sleeve 54 converges to outlet 56. The diameter of outlet 56 is a little greater than the diameter of throat 16. A plurality of circumferentially spaced keys 61 extend longitudinally in sleeve 54 and project radially into bore 58. Screw 22 extends through the stator sleeve, and keys just clear this screw.

When the sawdust clears throat 16 of sleeve 11, it passes through the enlarged entrance 55 of stator sleeve 54 so that it is free to expand a little at this point. As the sawdust travels along the stator sleeve, it begins to be compressed as a result of the action of an extrusion die, described later, in communication with said sleeve. The build-up of pressure as the sawdust travels along the sleeve results in excess moisture in the form of water being squeezed from it, and this liberated water moves away from the high pressure zone near outlet end 56 and in fact travels counter to the movement of the sawdust. It is believed that this water travels in the lee of keys so with reference to the direction of rotation of screw 22. As the screw charged with sawdust completely fills throat 16, water cannot travel back into extrusion sleeve 11. One or more openings are provided at the entrance end of stator sleeve 54 to permit the water to flow out of said sleeve. In the illustrated example of the invention, end 15 of sleeve 11 is formed with a bevel 62 on its outer surface, while sleeve 54 is formed with a corresponding bevel 63 on its inner surface at the entrance end thereof. Actually, the bevel surfaces 62 and 63 are spaced from each other to create an annular outlet 65 for the passage of the water. It will be noted that annular outlet 65 in cross section extends from stator sleeve 54 rearwardly with respect to the direction of movement of the sawdust and outwardly of said sleeve, see FIGURE 2. Some very fine sawdust may travel out of the apparatus with the water, but this arrangement of the annular outlet cuts the amount of sawdust escaping With the water to a minimum.

A worm wheel 63 surrounds sleeve 11 and is carried by suitable bearings 69 and 70 within gear box d. This worm wheel is driven by a worm 70 having a shaft 71 projecting from the gear box, said shaft being turned by a suitable source of power, not shown. Worm wheel 68 is connected to a blade disc 72 having curved radial impeller blades 73 extending normally from its downstream face and surrounding the annular outlet passage 65 between sleeves 11 and 54. When worm wheel 68 and disc 72 are rotated, blades 73 discharge water received from annular passage 65 outwardly through an outlet 74 in gear assembly housing 59, see FIGURE 6. Ports 72a in disc 7?. permit any water caught in annular space 72b to be flung from said annular space by centrifugal force, thereby preventing said water from creeping along the outer surface of sleeve 11.

If desired, suitable means may be provided for keeping outlet 65 clear of fine particulate material moved through said outlet by the water travelling therethrough, although this is not absolutely necessary. For this purpose, a suitable fiuid, such as air, steam, water and the like, may be directed against the water emerging from outlet 65 to direct said water and any fine material therein clear of the outlet. An annular chamber 75 is formed in the end cover 75a of gear box assembly 50 and surrounds stator sleeve 54. A flat ring or cover 76 lies between this chamber and fan blades 73, see FIGURE 2. Cover 76 has a plurality of small jets 77 formed therein adjacent and surrounding outlet 65, said jets extending from chamber 75 generally inwardly towards the outlet. A suitable fluid is directed into chamber 75 through an inlet 78.

Jets 77 are arranged to direct fluid under pressure across outlet 65 where the water expressed from the feed material emerges therefrom. This prevents any fine material in the water clogging or obstructing the outlet 74.

An extrusion die 79 abuts against the discharge end of stator sleeve 54. A key 80 fits in keyway 81 formed in end cover 75a, stator sleeve 54 and die 79 to prevent the latter from rotating. Die 79 is formed with a smooth bore 82, the diameter of which is less than that of stator sleeve bore 58 at the outlet end 56.

The abutment joint between die 79 and sleeve 54 is such that the bores are co-axially located and there is no tendency for material to pass between the mating surfaces. This is accomplished by having approximately tapered mating abutment faces 83 arranged to converge in the direction of flow. It is desirable to provide die 79 with a further short tapered surface 84 whose larger entrance diameter is the same or slightly greater than the discharge end 56 of stator sleeve 54, the smaller end blending into the bore 82 of die 79. The cross sectional shape of bore 82 determines the cross sectional shape of the fuel logs formed with this apparatus. The most common cross sectional shape is circular.

It will be noted that screw 22 extends through the stator sleeve and has an end 88 just within bore 82. The spiral part of screw 22 has a substantially flat portion or pressureface 89 at the screw end 88.

The sawdust is compacted in the bore of extrusion die 79. This compaction in the die causes the compres sion of the feed material in stator sleeve 54 as mentioned above. As screw 22 rotates, the flat pressure face 89 continually lays down a thin layer of plastic material, which is the state of the feed material at this time. This plastic state results from pressure, heat and chemical action in thepresence of the moisture. The diameter and length of this die are such as to create the major portion of the necessary back pressure to produce the required heat and a desired compaction of the material. In addition to this, die 79 must be long enough to permit the material to flow inwardly and fill the hole at the centre left by the core of screw 22.

The sawdust is subjected to considerable high pressure as the screw discharges it and lays it down on the end of the log formed in the die 79. As the feed sawdust is laid down, friction of the screw rubbing on the compacted log in the die produces heat. This heat increases the temperature of the feed material to some point above the normal boiling point of water. The extrusion screw generates its pressure in the region around the end 88 and pressure face 89 thereof, and as the feed material is laid down, it is subjected to a high pressure and heat. As the pressure face moves over the adjacent surface of the log in die 79, this pressure is suddenly released, resulting in the superheated moisture flashing and disintegrating the ligno-cellulosic particles of the feed. This pressure release results from the fact that pressure face 89 is the end of the spiral portion of screw 22 and therefore fonns a slight shoulder on the end of the screw, and when said face clears sawdust on the log surface the pressure on said sawdust is momentarily released with the subsequent flashing and disintegrating action. On the next revolution of the screw, these disintegrated particles are again laid down on the log in the die at the same time as more feed is laid down to be flashed, and so repeats the process. As the compacted mass is moved through die 79 by the action of the screw, the solid log is formed. Chemical constituents of the wood are activated by the temperature, pressure and moisture content present at the end of the screw.

tubes is to cool and fix the logs before they are discharged. A secondary function is to progressively reduce circumferential restraints on the log. The combined lengths and diameters of these cooling tubes must provide adaquate residence time for cooling, and, in conjunction with the die, must produce the correct back pressure to generate suitable conditions at the die entrance for forming a log.

FIGURE 3 shows parallel-bore cooling tubes and 96. These tubes usually are cooled by circulating water through concentric water jackets 97 and 98.

Cooling tube 95 abuts against the discharge end of the die 79. Its bore diameter is slightly greater than that of the die, and the joint between them is such that there is no tendency for material to pass between the mating surfaces. This is accomplished by having appropriately tapered mating abutment faces 101 arranged to converge in the direction of flow. This arrangement allows the smaller-diameter upstream tube to project slightly into the larger downstream tube, thereby masking the joint and providing perfect alignment. Tube 96 has the same joint arrangement with tube 95, and the inner diameter of the former is increased over that of the latter. There may be any desired number of these cooling tubes. The bores of all of the cooling tubes and the die preferably have a fine surface finish and are hard-chrome plated.

Die 79 and tubes 95 and 96 are held in place in alignment with stator sleeve 54 in any convenient manner. In this example, a plurality of long steel bolts 105 extend through a flange 106 formed on the outer end of tube 96 (see FIGURE 1) and are threaded into the end 107 of housing 34, see FIGURE 2.

The restraint offered by the cooling tubes to axial movement of the log combined with that of the die constitutes the back pressure necessary to produce a satisfactory log. This back pressure is conjunction with the required cooling residence time can be achieved by suitable combinations of tube lengths and diameters. If desired, fine adjustment of back pressure can be controlled by introducing a short length of tube which has an adjustable bore.

This tube may be inserted anywhere in the extrusion sys-' tem after the die where is functions satisfactorily.

Sleeve 11, stator sleeve 54, and extrusion die 79 form a main passage through which the feed material is moved by extruder screw 22. Die 79 constitutes a restricted outlet for said passage. The fuel log is formed in said die, and the back pressure in the feed material as the latter is moved against the end of the formed log causes the material to be compressed in the passage, resulting in excess moisture being squeezed from said material. Outlet 65 forms passage means at the main passage through which the expressed water escapes therefrom without interfering with the movement of the material.

What I claim as my invention is:

1. Apparatus for producing fuel logs from wet lignocellulosic material in particulate form, comprising coaxially arranged feed and stator sleeves and a tubular die forming a continuous passage, means for admitting particulate material to the feed sleeve, said stator sleeve having an outlet end no smaller in cross section than the die and in communication therewith and diverges from said outlet end to an entrance end of larger cross section than said outlet end and a discharge end of the feed sleeve in communication with said entrance end, a plurality of circumferentially spaced keys in the stator sleeve and extending longitudinally thereof, said keys having inner faces extending substantially parallel with a central longitudinal axis of said tubular die, a parallel-sided feed screw extending through the feed and stator sleeves to the tubular die, said screw rotatably fitting in the stator sleeve keys and the discharge end of the feed sleeve, and an annular outlet from the stator sleeve near the entrance end thereof, said outlet extending rearwardly in cross section from the stator sleeve to permit moisture expressed from wet ligno-cellulosic material to flow out of the apparatus.

2. Apparatus for producing fuel logs from wet lignocellulosic material in particulate form, comprising an extrusion die having a passage bore extending therethrough, a stator sleeve having an internal passage bore coaxial with and in communication with the die bore,'said sleeve bore having an outlet end no smaller than the die bore in cross section, said sleeve bore diverging outwardly slightly in a direction away from said outlet end, a plurality of circumferentially spaced keys carried by the sleeve and extending longitudinally thereof and projecting into the sleeve bore, said keys having inner faces extending substantially parallel with a longitudinal central axis of the die bore, a feed sleeve aligned and in communication with said stator sleeve, means for admitting particulate material into the feed sleeve, a parallel-sided feed screw extending through the feed sleeve and the stator sleeve bore to the die bore rotatably fitting within the feed sleeve and just clearing said keys, outlet means in and extending outwardly from the stator sleeve spaced rearwardly of said outlet end to allow moisture expressed from Wet ligno-cellulosic material to escape from the stator sleeve without interfering with the movement of the material through the stator sleeve and die bores, said screw having an end in the die bore with a pressure face thereon forming a slight shoulder on the screw end.

3. Apparatus for producing fuel logs from wet lignocellulosic material in particulate form, comprising wall means forming a passage having an inlet end and a discharge end and through which particulate material is moved from said inlet end towards said outlet end to form a continuous compacted fuel log, an extrusion die section forming part of said passage and having a smooth bore of a cross-section substantially equal to that desired in the produced fuel log, a stator section forming part of the passage ahead of the die section with reference to the direction of movement of particulate material, said stator section having an outlet end communicating with and substantially the same cross-section as the die section bore, said stator section diverging towards the passage inlet end from said outlet end thereof to an entrance end of a crosssection a little greater than the outlet end cross-section, slot means in the wall means of the stator section extending from the outlet end to the entrance end of said stator section and opening into said passage throughout the length of the stator section, restricted outlet means in said wall means communicating with said slot means at the entrance end of the stator section and opening out from the apparatus, a feed section in said passage extending to and communicating with the entrance end of the stator section, said feed section having a reduced throat at said stator section entrance of a cross-section substantially equal to that of said stator section outlet end, means for admitting particulate material into the feed section near the inlet end of said passage, and pressure means forcing particulate material in a mass through said passage, said die section creating back pressure in the material in the passage while forming the log to cause moisture to be expressed from the material in the stator section into said passage means and out of the apparatus through said outlet means, and said reduced throat preventing the expressed moisture from entering said feed section.

4. Fuel log producing apparatus as claimed in claim 3 in which the pressure means comprises an extruder screw in said passage extending through the feed and stator sections and terminating in the die section adjacent the outlet end of said stator section, said screw having an end in the die section with a pressure face thereon forming a slight shoulder on the screw end.

5. Fuel log producing apparatus as claimed in claim 4 in which the screw is parallel-sided and is of a die just to clear the diameter section bore, stator section outlet end and the reduced throat of the feed section.

6. Fuel log producing apparatus as claimed in claim 5 including a plurality of circumferentially spaced keys on the wall means in and extending longitudinally of the feed section, said keys terminating at the reduced throat of said feed section, and said screw just fitting within said keys.

7. Fuel log producing apparatus as claimed in claim 4 in which said passage means is formed by a plurality of circumferentially spaced keys on the wall means in and extending longitudinally of the stator section, said screw just fitting within said keys throughout the length of the latter.

8. Fuel log producing apparatus as claimed in claim 4 including cooling tube means having a bore aligned and in communication with said die section bore, said bore of the cooling tube means having an entrance at said die section of substantially the same diameter as the die section bore and in a direction extending away from the die section, and cooling means within said cooling tube means, said cooling tube means receiving a formed log from the die section and maintaining complete circumferential restraint on said log while the surface of the latter is being cooled by said cooling means.

9. Fuel log producing apparatus as claimed in claim 4 including impeller means outside said passage and at said outlet means for directing moisture flowing outwardly therefrom away from said outlet means.

10. Fuel log producing apparatus as claimed in claim 4 including means outside said passage and near said outlet means for directing fluid under pressure past said outlet means to blow liquid and particulate material emerging therefrom away from aid outlet means.

(References on following page) UNITED 7 References Cited by the Examiner 2,769,201 2,770,837

ST-ATES PATENTS 2833633 Pnce 159-2 Steinle 18-12 Millington 18-475 X 1,253,139 Brown et a1. 627,048 Bowling 18-12. Uschmann. Croston et a1.

Roy

11/1956 Lorenian 18-13 11/ 1956 Reifenhauser 18-12 5/ 1958 Hecht 18-475 X FOREIGN PATENTS 12/1960 France.

3/1936 Germany.

DANIEL E. WYMAN, Primary Examiner.

1847 5 10 ROBERT F. WHITE, Examiner. 

1. APPARATUS FOR PRODUCING FUEL LOGS FROM WET LIGNOCELLULOSIC MATERIAL IN PARTICULATE FORM, COMPRISING COAXIALLY ARRANGED FEED AND STATOR SLEEVES AND A TUBULAR DIE FORMING A CONTINUOUS PASSAGE, MEANS FOR ADMITTING PARTICULATE MATERIAL TO THE FEED SLEEVE, SAID STATOR SLEEVE HAVING AN OUTLET END NO SMALLER IN CROSS SECTION THAN THE DIE AND IN COMMUNICATION THEREWITH AND DIVERGES FROM SAID OUTLET END TO AN ENTRANCE END OF LARGER CROSS SECTION THAN SAID OUTLET END AND A DISCHARGE END OF THE FEED SLEEVE IN COMMUNICATION WITH SAID ENTRANCE END, A PLURALITY OF CIRCUMFERENTIALLY SPACED KEYS IN THE STATOR SLEEVE AND EXTENDING LONGITUDINALLY THEREOF, SAID KEYS HAVING INNER FACES EXTENDING SUBSTANTIALLY PARALLEL WITH A CENTRAL LONGITUDINAL AXIS OF SAID TUBULAR DIE, A LPARALLEL-SIDED FEED SCREW EXTENDING THROUGH THE FEED AND STATOR SLEEVES TO THE TUBU- 